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# PH - W/E/Momentum

### Physics: Work, Energy, and Momentum - KAPLAN/MCAT in a box

Question | Answer |
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Center of Gravity | The point on some object or body at which the entire force of gravity is considered to act on the object. |

Center of Mass | The point on some object or body at which all of its mass is considered to be concentrated. |

Completely Elastic Collision | Type of collision in which both momentum and kinetic energy are conserved. That is, the sum of the initial kinetic energies right before the collision equals the sum of the final kinetic energies just after the collision. |

Completely Inelastic Collisions | Type of collision in which the two bodies stick together after colliding, resulting in one final mass and velocity. Momentum is conserved but kinetic energy is not. |

Conservation of Mechanica Energy | When only conservative forces act on an object and work is done, energy is conserved and described by the equation: ΔE = ΔKE + ΔPE = 0. |

Conservation of Momentum | The momentum of a system remains constant when there are no net external forces acting on it. |

Conservative Force | A force, such as gravity, that performs work over a distance that is independent of the path taken. |

Impulse | Often denoted by j, it is the change in momentum, given by Δp. |

Kinetic Energy | The energy of an object in motion, calculated by the equation KE = 1/2 mv^2 and given in the SI unit of Joules (J). |

Momentum | Often denoted by p, it is a vector quantity given by an object's mass times its velocity. |

Nonconservative Force | A force, such as friction, that performs work over a distance that is dependent on the path taken between the initial and final positions. |

Potential Energy | The energy of an object due to its height off ground level, calculated by the equation PE = mgh. |

Power | The rate at which work is done, given given by the equation P = W/Δt, where W is work and t is time (in seconds). |

Work | The quantity measured when a constant force acts on a body to move it a distance d, calculated by the equation W = F d cosθ, where cosθ indicates that only the component of the force parallel to the direction of motion is considered. |

Work-Energy Theorem | A theorem stating that the net work performed on an object is related to the change in kinetic energy of that body, given by the equation W = ΔKE. |